Figure 4.

Cs⁺ and Ba²⁺ inhibit Rb⁺ uptake in plants grown in the absence of K⁺ and the presence of 5 mm NH₄⁺. Relative effect of CsCl (100 μm) and BaCl₂ (1 mm) on the uptake of Rb⁺(⁸⁶Rb) in plants exposed for 3 d to the absence of K⁺ and the presence of both 5 mm NH₄⁺ and 100 μm Na⁺. Rb⁺(⁸⁶Rb) uptake was measured at 100 μm Rb⁺ in the absence of NH₄⁺ and the presence of 100 μm Na⁺. On the left, the uptake of Rb⁺(⁸⁶Rb) measured in the absence of inhibitors is shown. Results are from an experiment consisting of five independent replicates. The presence of the same letter on two columns indicates the absence of significant differences at P = 0.05.